1. Field of the Invention
The present invention relates generally to the field of template devices that may include a variety of shapes, letters, numbers, and/or symbols, and measuring devices which fold for compact carrying and storage. More specifically it relates to a folding and latching drafting aid including an elongate planar member in the form of a ruler and template of hard, flexible and resilient material having a first side and a second side and two planar member ends, a central hinge structure about which the drafting aid folds and a latch structure which selectively locks the planar member ends together. The central hinge structure is preferably a molded groove extending laterally across the first side of the planar member which serves as a living hinge that avoids material fatigue and thus permits the planar member to fold as a result of its narrow cross-section so that the second side of the planar member is brought face to face against itself. The latch structure preferably includes first and second latch ports cut out of the planar member ends which are positioned so that the ports register with each other when the planar member is folded. Within the first latch port is a first locking tab protruding from the outer end of the port and toward the hinge. This locking tab is recessed from the first side of the planar member to be thinner and more flexible than the planar member. Within the second latch port is a second locking tab protruding from the inner end of the port and away from the hinge, and also recessed from the first side of the planar member for greater flexibility. When the planar member is folded, and the first and second ports register, the first and second locking tabs are overlapping and mutually parallel. To latch the drafting aid in the folded position, a method is provided wherein one tab is pressed against the other tab so that both tabs bend in the pressed direction and the pressed tab snaps over the other, retaining tab. The tabs remain in this crossed over, latching relationship and thereby hold the drafting aid folded until the pressed tab is pressed in the opposite direction through the opposing port to cause the pressed tab to snap back over the free end of the retaining tab so that the tabs no longer interlock. The pressed tab is preferably longer than the retaining tab for easier latching. It should be noted that the longer, pressed tab is easier to latch not only because it is longer than the shorter, retaining tab, but it is also parallel to the shorter retaining tab in the unlatched position. On the other hand, the longer, pressed tab is more difficult to unlatch than it is to latch because in the latched position, the two tabs are no longer parallel to each other, and thus the longer, pressed tab must travel a greater distance to reach the unlatched position, parallel to the retaining tab.
The planar member preferably has a series of template openings spaced axially along its length and cut into a variety of geometric shapes, such as a circle, a square and a triangle, to permit tracing of these shapes with a marking instrument. The longitudinal edges of the planar member may be used as guides to draw straight lines which are not interrupted crossing the living hinge. That is, a straight line may be drawn along the entire length of the drafting aid in its unfolded configuration. This drafting aid design permits drafting aid manufacture by single action molding.
2. Description of the Prior Art
There have long been templates and measuring devices which fold into a compact form for carrying and storage.
One such device is that of Greene, U.S. Pat. No. 2,555,741, issued on Jun. 5, 1951. Greene teaches a collapsible ruler formed of a strip of fabric having a series of spaced apart stiff rib segments attached along its length. The rib segments cause the ruler to fold only at the spaces between the rib segments and thus to collapse in an accordion configuration for storage. A problem with Greene is that no provision is made to keep the folded ruler from accidently falling open or otherwise unfolding at the wrong moment. Another problem with Greene is that the fabric strip would not have sufficiently firm edges to permit drawing straight lines against the edges. Furthermore, the rib segments would obstruct any template shape openings which might be cut into the strip.
Libit, U.S. Pat. No. 4,987,685, issued on Jan. 29, 1991, discloses a foldable accounting guide. The Libit guide includes a panel marked with guide line markings and having a folding construction. The folding construction includes a hinge structure having a triangular component with angularly disposed hinge axes between a triangular connecting member and two end components. This arrangement permits the end components to be oriented in perpendicular relation, in overlapping relation, or in longitudinal relation. A problem with Libit is once again that no provision is made to hold the foldable guide in a folded configuration. Another problem is that the general shape is needlessly wide and awkward for use as a ruler.
Bilodeau, et al., U.S. Pat. No. 4,565,012, issued on Jan. 21, 1986, reveals a marking and measuring instrument. Bilodeau et al. includes a series of rectangular plates hingedly joined together sequentially along their longitudinal edges to form a composite panel. A cut extends through the plates at an angle across the composite panel and is spanned by hinge means. Bilodeau et al. is wrapped around cylindrical and other three-dimensional objects to provide perimetrical measurements of the outer surfaces of the objects. The composite panel may be provided with measuring indicia. A problem with Bilodeau et al. is that there is no provision for holding the apparatus in a folded configuration, and unwanted deployment is therefore likely. Another problem is that even if folded, Bilodeau et al. is bulky, and would be relatively expensive to manufacture.
Giroux, U.S. Pat. No. 4,203,227, issued on May 20, 1980, reveals a telescopic straight edge for use in construction. Giroux includes several elongate slat members joined together end to end so that their longitudinal edges lie in common parallel planes with all edges in a first or a second common plane. Conventional pin hinges join ends of several slat members together in series so that the apparatus can fold. Each outer slat member has a longitudinal dovetail groove which telescopingly receives a longitudinal dovetail rib on a sliding slat member sized to slidingly engage the groove. A problem with Giroux is that no provision is made to hold the straight edge in a folded configuration. Another problem is that Giroux would be relatively expensive to manufacture with its separately formed and attached hinges and its complex slat members.
Evans, U.S. Pat. No. 3,792,511, issued on Feb. 19, 1974, teaches a document clamp formed of a series of four slat members. The middle two slat members are inter-connected end to end by a hinge, and the outer two are connected to the middle two by pivot pins. Evans includes cooperative magnet elements at the outer ends of the middle and outer slat members which come face to face and magnetically engage when the slat members are hinged and laterally pivoted closed. In use, Evans folds around edges of blueprints and documents to hold them in place, and may include measuring indicia along its longitudinal edges. A problem with Evans is that the magnet elements could erase dictation tapes if by chance placed next to them on a desk. Another problem is that the manufacture and assembly of hinges and magnetic elements make Evans expensive.
Ferguson, U.S. Pat. No. 3,503,130, issued on Mar. 31, 1970, reveals a folding ruler. Ferguson includes two or more slat members connected end to end by hinges, parts of which are molded into the slat members themselves. Each slat member end has a series of laterally spaced apart, coaxial tube portions extending therefrom, which mesh with tube portions of an adjacent slat member when the slat members are fitted end to end so that the tube portion inner passageways align and permit the insertion of a hinge pin. A problem with Ferguson is that the formation of tube portions on the slat member ends would require expensive and complex molding or machining. Another problem is once again that no provision is made to hold the ruler in the folded position.
Quenot, U.S. Pat. No. 3,289,302, issued on Dec. 6, 1966, discloses a folding measuring instrument. Quenot includes rigid elongate elements pivotally secured endwise with rivets and marked with scales. A plastic spring is provided on the pivotal connection between any two successive elements, each spring including a male and a female section on opposing element faces, so that the springs removably snap over and engage each other when the elongate elements are folded face to face. A problem with Quenot is that these spring elements cannot be economically manufactured in a single action molding process.
It is thus an object of the present invention to provide a drafting aid apparatus which folds at a hinge structure into a flat, completely flush, compact configuration, and which easily and reliably latches in the folded configuration.
It is another object of the present invention to provide such an apparatus which provides longitudinal line tracing guide edges in its unfolded configuration which are not irregular at the hinge structure, which is useful in the folded configuration as well.
It is still another object of the present invention to provide such an apparatus which is sturdy and reliable, and which preferably provides template openings for tracing various shapes with a marking instrument.
It is finally an object of the present invention to provide such an apparatus which is relatively inexpensive to manufacture and which can specifically be manufactured with a single action molding process.